Also in my garage: classic cars and slide rules

“The calculation to check the amount of beer in a barrel was very complicated, especially because the barrels differed in size and the liquids varied,” he continues.

“There was no such thing as an imperial gallon and each product had its own measurement.”

Slide rules don’t take up as much space as cars. Or books.

There are drawers and drawers of them in Butler’s study, some of them extremely rare.

Butler sees a direct link between his love for slide rules and for classic cars, such as the MG TD he’s had since his youth

Butler shows one that has four sliding elements and then another that has six. “There are only two of these known to exist,” he says.

Butler has slide rules used to calculate the weight of powder required in cannons aboard naval ships, slide rules for working out trajectories for artillery shells and gunshot on land, and slide rules for working out longitude at sea.

“Many people will be familiar with John Harrison and his marine chronometer that enabled sailors to calculate longitude,” says Butler, “but these early clocks were so expensive that even the Royal Navy couldn’t afford them, so an analogue solution was needed.”

The electronic calculator was the slide rule’s downfall, and Butler has amassed a respectable collection of those, too

Most of Butler’s early slide rules are made from wood, the majority manufactured in the heart of slide-rule production in the Southwark area of south London.

A few early ones are in white ivory.

“James Watt, the inventor, thought it was crazy to have so many different slide rules, so he designed one that could be used to solve multiple problems,” explains Butler.

“The ones I’ve got might not have been used by Watt himself, but probably came from his workshops.”

An analogue chronometer is part of Butler’s varied collection

Not surprisingly, the slide-rule industry disappeared overnight with the invention of the electronic calculator. Here we see some dangerous hobby creep, because Butler also appears to have a respectable collection of those.

“That one,” he says, pointing to a rather basic-looking machine, “was the first commercially available Texas Instruments calculator.”

Another is a calculator used by Soyuz astronauts in the late 1970s and early ’80s.

No Enigma machine? “I’d like one,” admits Butler, “but I’m not sure that the lady of the house will tolerate me spearing off in yet another direction.”

Butler attributes a fascination for engineering to his interest in slide rules

So why this obsession with scientific instruments, and slide rules in particular? “I’ve always been fascinated by engineering and by its evolution,” says Butler.

“Of all the cars I’ve owned, the Bugatti is my favourite because I find Ettore Bugatti and his approach to engineering and his commitment to high standards totally absorbing.

“I think there’s a direct link from the highly intelligent mathematicians and engineers, such as James Watt, who created many of these instruments and used them in practice, to 20th-century pioneers such as Bugatti.”

Images: Luc Lacey

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